1. Field of the Invention
The present invention relates to methods of and apparatus for the processing of drilling fluids. In another aspect, the present invention relates to drilling fluid processing apparatus and methods for processing drilling fluids. In even another aspect, the present invention relates to shale shakers for processing drilling fluids, and to methods of processing drilling fluids with shale shakers. In still another aspect, the present invention relates to shale shakers having a stair-stepped (or cascade) shaker screen deck arrangement, and to methods of processing drilling fluids using such shale shakers, and to methods of retrofitting shale shakers. In yet another aspect, the present invention relates to shale shakers having a stair-stepped shaker screen deck arrangement arranged in a manner that will protect the seals from the direct flow of fluids/solids, and to methods of processing drilling fluids using such shale shakers.
2. Brief Description of the Related Art
In the drilling of a borehole in the construction of an oil or gas well, a drill bit is arranged on the end of a drill string, which is rotated to bore the borehole through a formation. A drilling fluid known as “drilling mud” is pumped through the drill string to the drill bit to lubricate the drill bit. The drilling mud is also used to carry the cuttings produced by the drill bit and other solids to the surface through an annulus formed between the drill string and the borehole. The density of the drilling mud is closely controlled to inhibit the borehole from collapse and to ensure that drilling is carried out optimally. The density of the drilling mud affects the rate of penetration of the drill bit. By adjusting the density of the drilling mud, the rate of penetration changes at the possible detriment of collapsing the borehole. The drilling mud may also carry lost circulation materials for sealing porous sections of the borehole. The acidity of the drilling mud may also be adjusted according to the type of formation strata being drilled through. The drilling mud contains inter alia expensive synthetic oil-based lubricants and it is normal therefore to recover and re-use the used drilling mud, but this requires inter alia the solids to be removed from the drilling mud. This is achieved by processing the drilling mud.
This need for solids control in drilling mud in hydrocarbon well drilling is well known in the prior art. Generally, at the top of the well, the solids-laden mud is introduced to a shale shaker, a device which typically has a series of screens arranged in tiered or flat disposition with respect to each other. The screens catch and remove solids from the mud as the mud passes through them. If drilled solids are not removed from the mud used during the drilling operation, recirculation of the drilled solids can create viscosity and gel problems in the mud, as well as increasing wear in mud pumps and other mechanical equipment used for drilling. In some shale shakers a fine screen cloth is used with the vibrating screen. The screen may have two or more overlying layers of screen cloth. The frame of the vibrating screen is resiliently suspended or mounted upon a support and is caused to vibrate by a vibrating mechanism, e.g. an unbalanced weight on a rotating shaft connected to the frame. Each screen may be vibrated by vibratory equipment to create a flow of trapped solids in either direction on top surfaces of the screen for removal and disposal of solids. The fineness or coarseness of the mesh of a screen may vary depending upon mud flow rate and the size of the solids to be removed.
Certain prior art screens have sealing members along opposed sides of the screens to seal downwardly against or upwardly against a mounting surface, e.g. a screen mounting member such as a “C” shaped channel. In other prior art devices, the screens are pressed against seals which are disposed on and/or secured to the mounting apparatus; in one device this is done on four sides of a rectangular screen.
A particular problem is encountered when two or more screens are abutted together in a linear arrangement to form a deck of screens. Vibration is introduced to urge the flow of solids containing fluids across the deck one screen at a time. While there certainly are seals between the abutted screens, as the particles traverse between the screens and over the seal abutted there between, a certain amount of particles is retained in the small recesses between the seal and the screens. The extreme vibrating environment causes all sorts of movement of the screen, seals and particles relative to each other. Over time, in this vibrating environment, the particles will work their way past the seals, even if the seal is intact and properly seated. In addition, between the corrosive action of the vibrating particles against the seals abrading the seals, and the harsh effect of the oil based fluids eating away on the seals, the integrity of the seal is slowly compromised.
In addition to a linear multi-screen deck arrangement, there is also a prior art stair-stepped (or cascade) deck in which the screens are stair stepped. In such a stair-step arrangement, an upstream desk discharges onto a subsequent screen that is positioned to receive the discharge. However, the configuration generally provides the discharge directly onto the seal positioned on the end of the subsequent screen. This too results in a certain amount of particles by-passing the seals and falling through.
There are a number of patents and publications which relate to shale shakers.
U.S. Pat. No. 5,392,925 issued to Seyffert on Feb. 28, 1995, discloses a vibratable shale shaker screen is disclosed which in one aspect, has a frame, screening material secured over the frame, and one or more sealing members secured to the frame for sealingly contacting an adjacent frame and/or adjacent portions of the frame or of screen mounting apparatus such as mount channels on the frame. Alternatively, sealing elements are provided on screen mounting apparatus, e.g. channels, on a shale shaker. A shale shaker is disclosed with at least one such screen. In one aspect such a shale shaker has three such screens disposed in a tiered configuration, one screen in sealing contact with the next. Adjustable screen mounts are disclosed for releasably holding the screens in sealing contact with each other and with screen mounting apparatus.
U.S. Pat. No. 5,593,582 issued to Roff, Jr. on Jan. 14, 1997, discloses a shale shaker having two feeds, two screens, two mud outlets and a removable tray between the screens is disclosed. Each screen receives one feed and produces one outlet of cuttings and another outlet for separated mud for either bypass or direct feed to the mud tank or the other screen. The removable tray or trays facilitate the two screens acting in cascade. Valves are provided to control the overall flow rate to the shaker and to the lower level screen.
U.S. Pat. No. 5,641,070 issued to Seyffert on Jun. 24, 1997, discloses a shale shaker which, in one aspect, has one or more upper screens and one or more lower screens with an upper screen at a discharge end of the shale shaker and a lower screen disposed to receive material discharged from a discharge end of one of the upper screens. In one aspect a portion of a lower screen underlies the discharge end of the upper screen. In another aspect a solid flowback pan prevents material falling through the upper screen(s) from falling onto the lower screen(s); and, in another aspect, the pan prevents material on a top of the lower screen(s) from falling into a bottom sump of the shale shaker which receives material which has fallen through the screen(s).
U.S. Pat. No. 6,530,482 issued to Wiseman on Mar. 11, 2003, discloses tandem shale shaker having at least a base, at least one upper shaker screen, at least one lower shaker screen, a basket, an apparatus for vibrating the basket, at least one distribution conduit, a flowback pan, a flow director, and a distribution apparatus. The upper and lower shaker screens are releasably mounted on the basket. The at least one lower shaker screen is mounted at a level below the level of the at least one upper shaker screen and underlies the at least one upper shaker screen. The flowback pan is disposed between the at least one upper shaker screen and the at least one lower shaker screen and overlies at least a portion of the at least one lower shaker screen. The flowback pan directs the screened material passing through the at least one upper shaker screen to the at least one distribution conduit. The flow director selectively directs screened material flowing through the at least one distribution conduit (a) to the at least one lower shaker screen or (b) away from the at least one lower shaker screen. To operate the tandem shale shaker in parallel rather than in series, the distribution apparatus is set to selectively directs unscreened material to the at least one lower shaker screen. Further, the flow director directs the screened material from the at least one upper shaker screen away from the at least one lower shaker screen.
U.S. Pat. No. 6,662,952 issued to Adams on Dec. 16, 2003, discloses screen support for supporting screening material of a screen assembly for use on a shale shaker for separating components of material introduced thereto, the screen support having a body, a plurality of spaced apart holes through the body, each of said holes for receiving part of a fastener used for releasably connecting the screen assembly to a shale shaker; the screen support in certain aspects being a frame, a perforated plate, a strip support or a unibody structure; a screen assembly with such a support; such a screen assembly, in certain aspects, with a plastic grid or layer with corresponding fastener holes; a shale shaker with any such screen assembly; and methods of their use.
U.S. Pat. No. 6,769,550 issued to Adams on Aug. 3, 2004, discloses a shale shaker system for separating components of drilling fluid with solids entrained therein, the shale shaker system, in at least certain aspects, including a base, a screen mounting basket on the base, vibrating apparatus connected to the screen mounting basket for vibrating the screen mounting basket, the screen mounting basket having mounting structure for at least one screen assembly mounted on the mounting structure, the mounting structure having a body over which the at least one screen assembly is positionable, some components of the drilling fluid to be treated by the shale shaker flowable through the at least one screen assembly and through the body, at least one wear strip attached to the mounting structure, the at least one wear strip having a wear strip body, at least one upwardly projecting member projecting upwardly from the wear strip body, the at least one screen assembly including a screen support with screening material and at least one hole in the support sized, configured, and located for receiving the at least one upwardly projecting member of the wear strip body of the mounting structure and the at least one upwardly projecting member sized, located and configured for receipt within the at least one hole.
U.S. Pat. No. 6,863,183 issued to Schulte on Mar. 8, 2005, discloses a shale shaker for separating material, said shale shaker comprising a basket for supporting a screen assembly and a collection receptacle, the basket comprising two side walls, an end wall and an opening in the bottom of said basket, said basket having means to support screen assemblies for substantially covering said opening characterized in that said basket further comprises separating means in or on any of said walls for separating material. Preferably, further comprising directing means for directing separated material therefrom into said collection receptacle. The invention also provides a method for separating material using the shale shaker of the invention, a basket of the shale shaker of the invention and screen assemblies used in the shale shaker of the invention.
U.S. Pat. No. 6,868,972 issued to Seyffert on Mar. 22, 2005 discloses a vibratory separator including basket apparatus for holding screening apparatus, at least one upper screen apparatus in the basket, the at least one upper screen apparatus having a fluid exit end, at least one lower screen apparatus in the basket below the at least one upper screen apparatus, fluid flowable from the at least one upper screen apparatus down onto the at least one lower screen apparatus, flow diffusion apparatus mounted below the fluid exit end of the at least one upper screen apparatus and above the at least one lower screen apparatus, so that fluid flowing down from the at least one upper screen apparatus flows onto the flow diffusion apparatus and is diffused thereby, and vibrator apparatus for vibrating the basket and the screen apparatus therein.
U.S. Patent Publication No. 20050183994 published by Hensley on Aug. 25, 2005, discloses an integrated, transportable cuttings treatment system includes a multi-part shale shaker, preferably formed of six screens vibrated by at least one electric vibrator, and preferably four such vibrators. Solids are screen from drilling mud flowing onto the screens, and directed into a trough wherein is located a screw conveyor or augur. A pressure differential is developed across the screens to increase the flow rate of drilling mud through the screens.
U.S. Pat. No. 7,571,817 issued to Scott on Aug. 11, 2009, discloses a vibratory separator (in one aspect, a shale shaker) and methods for using it, the separator in certain aspects having a base, a basket movably mounted on the base, screen apparatus on the basket, material flowing onto the screen apparatus for treatment, at least a portion of the screen apparatus not inclined downhill (e.g. said portion horizontal or uphill), electromagnetic vibratory apparatus connected to the basket for vibrating the basket and the screen apparatus, driving apparatus for driving the electromagnetic vibratory apparatus, and control apparatus (on-site and/or remote) for controlling the driving apparatus and the electromagnetic vibratory apparatus; the material, in one aspect, being drilling fluid material with solids therein.
U.S. Pat. No. 7,581,647 issued to Grichar on Sep. 1, 2009, discloses a shale shaker or vibratory separator which, in one aspect, has a base, vibration isolation apparatus on the base, a basket, mount apparatus for mounting the basket on the base, and at least one of the base, basket, and the mount apparatus made of, encased in, or coated with composite material which, in certain aspects, is all or part flexible composite material; and methods of using such separators and shakers.
U.S. Patent Application 20100270216 published by Burnett on Oct. 28, 2010, discloses a shale shaker for separating solids from solids laden drilling fluid is disclosed as having a basket with a scalping screen deck, at least one first screen deck and at least one second screen deck. The basket further may have a flow tray arranged between said scalping screen deck and at least one first screen deck, and a plurality of first ducts and a plurality of second ducts, the plurality of first ducts for directing solids laden drilling fluid to the at least one first screen deck. The second plurality of second ducts are for directing solids laden drilling fluid to said second screen deck.
U.S. Patent Publication No. 20140021120 published by Burnett on Jan. 23, 2014, and U.S. Pat. No. 8,556,083 to Burnett issued Oct. 15, 2013, both disclose shale shakers with selective series/parallel flow path conversion. Specifically, methods and systems are disclosed employing a shale shaker for processing a mixture of drilling fluid and solids with multiple screen assemblies and conversion apparatus for switching flow to the screen assemblies between series flow and parallel flow; and in one aspect, a screen or screens for screening lost circulation material.
U.S. Pat. No. 8,869,986 issued to Bailey on Oct. 28, 2014, discloses screening methods and apparatus, particularly, an apparatus for use in screening a liquid and solids mixture feed comprises a conduit, including a screening portion that is formed and arranged to divide a liquid and solids mixture feed flowing through the conduit. The feed is divided into a first, cleaned stream comprising liquid and solid particles of below a selected size limit, and a second, concentrated, stream comprising liquid, and particles above the selected size limit. The apparatus may be a stand-alone module, part of a system with other solids and liquids separating equipment or an integral part of a solids and liquid separator such as a shale shaker. Methods of using the apparatus are also described.
However, in spite of the above advancements, there exists a need in the art for improved shale shakers and improved methods of processing solids containing fluids.
There also exists a need in the art for improved shale shakers to reduce or eliminate solids by passing the seals between abutted shaker screens arranged in a deck.
There even also exists a need in the art for improved shale shakers to reduce or eliminate the exposure of the screen seals to the processed fluids and/or solids.
There still also exists a need in the art for improved shale shakers to reduce or eliminate the degradation of the screen seals in the operation of the shale shaker.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.